Dryness increases predation risk in efts: support for an amphibian decline hypothesis
Dryness increases predation risk in efts: support for an amphibian decline hypothesis
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干旱增加了 efts 的捕食风险：支持两栖动物衰退假说
作者：
Jason Rohr;D. Madison
关于两栖动物数量减少的一种假设是，全球气候变化导致的干旱加剧使两栖动物面临更大的生物威胁，从而导致更高的死亡率。但是，我们对陆地两栖动物对干燥条件单独或与生物威胁相结合的行为反应知之甚少。我们利用实地观察和实验室实验来测试东部红斑蝾螈（Nototropicus viridescens）的陆生幼鱼对单独和组合干燥和捕食风险的反应。当只有面临干燥风险时，它们就会转移到阴凉处、下坡、减少活动并采取节水姿势。 Efts还显着降低了因挤在一起而导致的失水率，并且被同种efts的化学信号所吸引，但不是来自同种成虫的化学信号。因此，埃夫特有多种行为可以降低与气候变化相关的脱水风险。当仅面临捕食风险时，以成虫和 eft 蝾螈组织提取物（警报化学物质）为代表，eft 会减少其活动并避免来自这两个来源的警报提示。当暴露于干燥和捕食的综合风险时，efts 的活跃程度低于单独暴露于任一风险时，并且避免使用成体组织提取物，但不使用 eft 提取物。这些结果表明，在干燥条件下，同种组织提取物同时含有吸引性（挤作一团）和排斥性（与捕食者相关）的化学成分，这些化学成分会诱导抵消行为反应。这是第一项证明对同种漂洗剂和警报物质的湿度依赖性反应的研究，强调了在研究对同种气味和/或警报化学物质的反应时考虑环境湿度和动物水合作用的重要性。这些结果支持这样的假设：脱水风险升高可能会损害反捕食者行为并加剧两栖动物种群数量下降。
One hypothesis for amphibian declines is that increased dryness attributed to global climate change exposes amphibians to greater biotic threat and, consequently, greater mortality. But, little is known about behavioral responses of terrestrial amphibians to dry conditions alone or in combination with biotic threats. We used field observations and laboratory experiments to test the response of efts (terrestrial juveniles) of the eastern red-spotted newt, Notophthalmus viridescens, to separate and combined desiccation and predation risks. When only at risk of desiccation, efts moved into shade, traveled down slope, decreased activity, and adopted water-conserving postures. Efts also significantly reduced the rate of water loss by huddling and were attracted to chemical cues from conspecific efts but not from conspecific adults. Thus, efts have a variety of behaviors that reduce the risk of dehydration associated with climate change. When faced only with a predation risk, represented by adult and eft newt tissue extracts (alarm chemicals), efts reduced their activity and avoided alarm cues from both sources. When exposed to combined desiccation and predation risks, efts were less active than when exposed to either risk separately and avoided adult tissue extracts, but not eft extracts. These results suggest that under dry conditions, conspecific tissue extracts contain both attractive (huddling) and repulsive (predator-related) chemical components that induce offsetting behavioral responses. This is the first study to demonstrate moisture-dependent responses to conspecific rinses and alarm substances, underscoring the importance of considering environmental moisture and animal hydration in studies examining responses to conspecific odors and/or alarm chemicals. These results support the hypothesis that elevated dehydration risk may compromise anti-predator behavior and exacerbate amphibian population declines.